BRISTOL, Pa. (AP) - A major Pennsylvania-New Jersey bridge closed since Jan. 20 for repairs to a fractured beam has reopened in time for the Friday morning rush hour, transportation officials said.

The reopening of the 1.3-mile-long Interstate 276 bridge late Thursday was ahead of schedule. Last week, officials estimated it would reopen in a month."Given the number of experts who have inspected, tested and studied it over the last 49 days, it's safe to say this bridge is perhaps the most scrutinized structure in the nation and maybe the world," Pennsylvania Turnpike chief engineer Brad Heigel said.The bridge, which connects the Pennsylvania and New Jersey turnpikes, had been closed since a painting crew found a cracked 14-inch steel truss under a westbound travel lane on the Pennsylvania side. That section of interstate typically carries 42,000 vehicles daily.Earlier this week, workers ran a series of load tests to study the effectiveness of their repairs. Eight dump trucks carrying 40 tons were driven across the bridge while sensors detected the structure's reaction. The results showed the repaired bridge can support the weight of live traffic.Two improperly drilled holes, each approximately 1 inch in diameter and filled with weld material, were identified as the primary factors behind the fracture. But officials agreed it was likely not the only trigger. No other such weld-filled holes were found.Heigel said getting a definitive answer as to why the fracture happened "is akin to solving a 60-year-old mystery perpetuated by unseen offenders. We may never know for sure what all the factors were that caused the fracture."